10 Most Unusual Flowers

Flor de Muerto, a common Mexican perennial, is the closest thing nature has to a truly black flower. And "the flower of the dead" actually looks like it's dead. The tubular flowers hang downward from 6-foot [2-meter] stems in a seemingly wilted, withered state. The plant has black petals, black leaves, black fruit, black seeds and black pollen.

Though unusual, the black flower is far from rare. It's easily found growing on roadside embankments and pine or oak forests in the states of Hidalgo, Veracruz, Oaxaca and Chiapas as well as in Guatemala. In a 2003 study, Kenneth R. Markham and associates determined the combination of pigments and light absorption that allows Lisianthius nigrescens to achieve its black color. It's the only flower known to completely absorb all wavebands of both ultraviolet (UV) and visible light [source: Markham].

But the real mystery of the flower of the dead is how it survives in such profusion without the discernable aid of a pollinating animal. The second part of the Markham, et al. study was to determine what the "ecological consequences" of a black flower are.

The flower's form suggests that hummingbirds, moths or long-tongued bees would pollinate it. But the scentless black flower doesn't possess any attributes to attract these animals.

Color perception depends on pigments, light and, literally, the eye of the beholder. Humans, birds and insects see the colors of flowers differently. Bees have UV, blue and green color receptors. They're attracted to yellow and blue flowers, particularly those that reflect UV light. Researchers speculate that bees avoid the red flowers that attract hummingbirds because the flowers don't reflect UV light and bees don't process red. To a bee, these flowers would appear black. Moths, who do their pollinating work at night, seek out light colored, highly scented flowers. So how does L. nigrescens attract the type of animal that could pollinate it?

The researchers conclude that, "The problem of how this flower might attract the pollinators when it totally absorbs in both the UV and the visible [light] remains to be explained."